Refractive index measurement method, refractive index measurement apparatus, and optical element manufacturing method

Abstract

A refractive index measurement method uses an interference optical system which divides light from a light source having a plurality of discrete wavelengths into test light and reference light, causes the test light transmitted through the target to interfere with the reference light, and detect the interference light. The refractive index measurement method determines a first optical delay amount of the interference optical system so that a first and a second wavelength become adjacent to a wavelength corresponding to an extremal value of a phase of the interference light, measures phases of interference light at the first and second wavelengths at the first optical delay amount, and calculates a phase difference between a plurality of the discrete wavelengths at a predetermined optical delay amount using the first optical delay amount, the phases of the interference light at the first and second wavelengths to calculate the refractive index of the target.

Description

BACKGROUNDField of Art[0001]The present disclosure relates to a refractive index measurement method and a refractive index measurement apparatus for measuring the refractive index of an optical element.Description of the Related Art[0002]The refractive index of a molded lens changes with molding conditions. The refractive index of a molded lens is generally measured, after being processed into a prism, by the minimum deviation angle method or the V block method. This processing work requires labor and cost. The refractive index of a molded lens further changes with residual stress in the lens being released through processing. Accordingly, to measure the refractive index of the molded lens with sufficient accuracy, a nondestructive measurement technique is required.[0003]With the measurement method disclosed in H. Delbarre, C. Przygodzki, M. Tassou, D. Boucher, “High-precision index measurement in anisotropic crystals using white-light spectral interferometry”, Applied Physics B, 20...

AI Technical Summary

Benefits of technology

The patent text describes a method for measuring the refractive index of a target using an interference optical system. The system splits light into test light and reference light, which enter the target and interfere with each other. The refractive index of the target is measured by measuring the phase of interference light at different wavelengths. The method uses a first optical delay amount to determine the refractive index of the target. The technical effect of this method is to provide a precise and accurate way to measure the refractive index of optical elements, which can help in the manufacturing process of optical components.

Problems solved by technology

This processing work requires labor and cost.

This method requires a wideband high-intensity continuous spectrum light source, which is expensive.

A wideband high-intensity discrete spectrum light source is inexpensive, but is difficult to be used because the sampling frequency often becomes lower than the frequency of the interference signal.

Images